Fuel injectors of the related art, as are used e.g. in injection systems for gasoline engines, are constructed for example as solenoid valves having a solenoid and an armature, which is formed from a ferritic magnetic material and provided with a hard non-magnetic surface layer, e.g. made of chromium. Because of this construction, when building up and diminishing the magnetic field in operation, eddy current losses result and consequently a slowdown of the switching time or dynamics of the fuel injector. The manufacture of the armature is moreover very costly and complicated. In addition, the resistance against aggressive media such as ethanol or urea for example, which are increasingly contained in fuels, is insufficient to ensure a satisfactory durability of the injectors in countries with high fluctuations in fuel quality. Furthermore, in the future, the compliance with statutory regulations must be ensured especially with regard to the use of materials that represent health hazards.